docs: def prefix(prefix):
      """Returns a dictionary of all environment variables starting with
      the given prefix, lower cased and stripped.
      """
  
      d = {}
      e = lower_dict(environ.copy())
  
      prefix = prefix.lower()
  
      for k, v in e.items():
          try:
              if k.startswith(prefix):
                  k = k[len(prefix):]
                  d[k] = v
          except AttributeError:
              pass
  
      return d